Method and system for producing hydrocarbon fluid through a well with a sensor assembly outside the well casing

ABSTRACT

A method is disclosed for producing hydrocarbon fluids through a well having a well casing string with a casing section which is surrounded by an annular space which comprises a sensor assembly for measuring electromagnetic and/or other physical properties of solid and fluid materials within the annular space, in an underground formation surrounding the annular space and/or within the interior of the section of the casing string, wherein the sensor assembly is mounted on a body of swellable material, such as a swellable rubber or other elastomeric material, which is secured to the outer surface of said casing section and presses the sensor assembly against the inner surface of the surrounding underground formation after the casing string has been lowered into the wellbore.

BACKGROUND OF THE INVENTION

The invention relates to a method and system for producing hydrocarbon fluid through a well with a sensor assembly outside the well casing.

Such a method and system are known from International patent application WO 03/029614, which discloses a system for measuring pore pressure in a formation surrounding a well casing by a pressure sensor which is embedded in a cement sheath surrounding a steel well casing, and which sheath is fractured by a perforating gun to provide an open fluid channel between the sensor and the pores of the surrounding formation.

A limitation of the known system is that it is difficult to provide electrical power to the sensor and to transmit data from the sensor to surface and that the steel casing inhibits collection of electromagnetic data about several properties of fluid and solid materials in the surrounding formation.

It is an object of the present invention to provide a method and system, which alleviate these limitations.

SUMMARY OF THE INVENTION

In accordance with the invention there is provided a method of producing hydrocarbon fluids through a well having a well casing string with a casing section which is surrounded by an annular space which comprises a sensor assembly for measuring electromagnetic and/or other physical properties of solid and fluid materials within the annular space, in an underground formation surrounding the annular space and/or within the interior of the casing section, wherein the sensor assembly is mounted on or in the vicinity of a body of swellable material, which body is secured to the outer surface of the section of the casing string and is configured to swell against the inner surface of the underground formation surrounding the wellbore after the casing string has been lowered into the wellbore;

and the sensor assembly is configured to measure one or more of the following properties:

-   -   the pore pressure in pores of the formation adjacent to the         annular space;     -   the chemical composition of fluid in the pores of the formation         adjacent to the annular space;     -   the electrical resistivity and/or conductivity of the solid and         fluid materials in the formation surrounding the annular space;     -   the streaming and spontaneous potentials of the solid and fluid         materials in the formation surrounding the annular space;     -   the dielectric constant of the solid and fluid materials in the         formation surrounding the annular space;     -   changes in a cement lining arranged in the annular space,         including migration of any chemical contaminants through the         cement lining;     -   properties of a fluid flowing through the interior of the         non-magnetic section of the casing string;     -   deformation and/or tilting of the well casing string;     -   deformation, such as compaction and expansion, of the formation         surrounding the annular space;     -   stress in any solid materials in the annular space and the         formation surrounding the annular space; and     -   acoustic rock reflections.

The sensor assembly may be connected to an electrical and/or fiber optical data transmission conduit within the casing string by a wireless data and/or power transmission link, which transmits data and/or power through the wall of a non-magnetic or weakly magnetic casing section.

The wireless data and/or power transmission link may comprise at least one pair of substantially coaxial inductive couplers which each comprise a coiled electrical cable.

In accordance with the invention there is furthermore provided a system for producing hydrocarbon fluids through a well having a well casing string with a casing section which is surrounded by an annular space which comprises a sensor assembly for measuring electromagnetic and/or other physical properties of solid and fluid materials within the annular space, in an underground formation surrounding the annular space and/or within the interior of the casing section, wherein the sensor assembly is mounted on a body of swellable material, which body is secured to the outer surface of the section of the casing string and is configured to swell and press the sensor to the inner surface of the underground formation surrounding the wellbore after the casing string has been lowered into the wellbore.

These and other features, embodiments and advantages of the method and system according to the invention are described in the accompanying claims, abstract and the following detailed description of preferred embodiments disclosed in the accompanying drawings in which reference numerals are used which refer to corresponding reference numerals that are shown in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic longitudinal sectional view of a well equipped with a sensor assembly according to the invention;

FIG. 2 is a schematic three-dimensional view of the inductive couplings on the production tubing and casing sections in the vicinity of the sensor assembly; and

FIG. 3 is a schematic longitudinal sectional view of a well equipped with a sensor assembly according to the invention.

DETAILED DESCRIPTION OF THE DEPICTED EMBODIMENTS

FIG. 1 shows a crude oil and/or natural gas production well 1, which traverses a crude oil and/or natural gas containing formation 2.

The well 1 comprises a wellhead 3 which is located at the earth surface 4 and from which a well casing 5 and a tubing hanger 6 are suspended, from which tubing hanger 6 a production tubing 7 is suspended within the well 1.

A sensor assembly 8 is mounted in a support sleeve 9, which is secured to the outer surface of a casing section 5A of the well casing 5, which support sleeve 9 substantially fills an annular space surrounding the well casing 5 within a region where the well 1 traverses the crude oil and/or natural gas containing formation 2. A wireless power and/or signal transmission sleeve 10 is mounted on the outer surface of the production tubing 7 at the same depth as the support sleeve 9 and such that the sleeves 9 and 10 are substantially co-axial to each other.

The wireless power and/or signal transmission sleeve 10 is connected to a surface monitoring unit 11 via an electrical and/or fiber optical cable assembly 12 extending through the annulus between the production tubing 7 and well casing 5 and through the wellhead 3. Optionally the cable assembly 12 may be equipped with a sensor interface unit 13 and a subsea control module 14 if the wellhead 3 is located at the sea bottom 4. FIG. 2 shows in more detail and at a larger scale than in FIG. 1 that the support sleeve 9 is provided with an inductive coupler 15 which is connected to the sensor assembly 8 and that the wireless power and/or signal transmission sleeve 10 is provided with a second inductive coupler 16, which is connected to the cable assembly 12 by a power and/or signal transmission, amplification and/or conversion module 17. The tubing 7 is inserted into the non-magnetic casing section 5A as illustrated by arrow 18 such that the inductive couplers 15 and 16 are arranged substantially co-axially to each other and form a wireless electrical power and/or signal transmission link which connects the sensor assembly 8 via the cable assembly 12 to the surface monitor unit 11.

The presence of a non-magnetic casing section 5A between the inductive couplers 15 and 16 enhances the wireless transmission of electrical power and/or signals between the sensor assembly 8 and the power and/or signal transmission, amplification and/or conversion module 17 so that the sensor assembly 8 may be equipped with a significant amount of sensors, such as sensors which are configured to measure:

-   -   the pore pressure in pores of the formation adjacent to the         annular space;     -   the chemical composition of fluid in the pores of the formation         adjacent to the annular space;     -   the electrical resistivity and/or conductivity of the solid and         fluid materials in the formation surrounding the annular space;     -   the streaming and spontaneous potentials of the solid and fluid         materials in the formation surrounding the annular space;     -   the dielectric constant of the solid and fluid materials in the         formation surrounding the annular space     -   deformation and/or tilting of the well casing string;     -   deformation, such as compaction and expansion, of the formation         surrounding the annular space;     -   stress in any solid materials in the annular space and the         formation surrounding the annular space; and/or     -   acoustic rock reflections.

FIG. 3 shows a liner 30 arranged in a wellbore 31 wherein the annular space between the liner 30 and wellbore 31 is filled with cement 32 and a sensor assembly according to the invention. The assembly comprises a support sleeve 33, a pressure sensor 34 which is embedded in an intermediate permeable swellable elastomeric sleeve 35, and an upper and a lower swellable elastomeric sleeve 36 and 37 are arranged above and below the intermediate permeable elastomeric sleeve 35.

The upper, lower and intermediate sleeves 35-37 are configured to swell against the wellbore 31 such that they have the swollen shape as indicated by dotted lines 35A-37A after the cement slurry 32 has been injected and before the cement slurry 32 has been hardened. The upper and lower sleeves 36 and 37 are impermeable and thereby seal off the intermediate sleeve 35 and the pressure sensor 34 embedded therein from the cement body 32. The intermediate sleeve 35 has a permeability, preferably in the range of 1-10 mD, to allow the pressure sensor 34 to be in fluid contact with the fluid in the pores of the formation 38 surrounding the wellbore 31. The pressure sensor 34 is provided with a signal and power supply cable 39, which may be connected to an umbilical power and signal transmission cable assembly 40 by an inductive coupler 41 or another wireless or wired coupling assembly. The pressure sensor 34 shown in FIG. 3 is adequately isolated from the cement 32 by the swellable sleeves 36A and 37A and is in fluid contact with the fluid in the pores of the surrounding formation 38 via the permeable sleeve 35A which enables the pressure sensor 34 to accurately monitor the pore pressure of the fluid, such as crude oil, natural gas, oil shale and/or shale oil, in the pores of the formation 38 over a prolonged period of time. 

1. A method of producing hydrocarbon fluids through a well having a well casing string with a casing section which is surrounded by an annular space which comprises: a) providing in the well a sensor assembly for measuring electromagnetic and/or other physical properties of solid and fluid materials within the annular space, in an underground formation surrounding the annular space and/or within the interior of the casing section, wherein the sensor assembly is mounted on or in the vicinity of a body of swellable material, which body is secured to the outer surface of the casing section and is configured to swell against the inner surface of the underground formation surrounding the wellbore after the casing string has been lowered into the wellbore; and the sensor assembly is configured to measure one or more of the following properties: the pore pressure in pores of the formation adjacent to the annular space; the chemical composition of fluid in the pores of the formation adjacent to the annular space; the electrical resistivity and/or conductivity of the solid and fluid materials in the formation surrounding the annular space; the streaming and spontaneous potentials of the solid and fluid materials in the formation surrounding the annular space; the dielectric constant of the solid and fluid materials in the formation surrounding the annular space; changes in a cement lining arranged in the annular space, including migration of any chemical contaminants through the cement lining; properties of a fluid flowing through the interior of the non-magnetic section of the casing string; deformation and/or tilting of the well casing string; deformation, such as compaction and expansion, of the formation surrounding the annular space; stress in any solid materials in the annular space and the formation surrounding the annular space; and acoustic rock reflections; b) producing hydrocarbons from the well; and c) using the sensor assembly to sense one or more of the properties.
 2. The method of claim 1, wherein the sensor assembly is connected to an electrical and/or fiber optical data transmission conduit within the casing string by a wireless data and/or power transmission link, which transmits data and/or power through the wall of the non-magnetic section of the well casing string.
 3. The method of claim 2, wherein the wireless data and/or power transmission link comprises at least one pair of substantially coaxial inductive couplers which each comprise a coiled electrical cable.
 4. The method of claim 1, wherein the sensor assembly is mounted on a body of swellable elastomeric material.
 5. A system for producing hydrocarbon fluids through a well having a well casing string with a casing section which is surrounded by an annular space which comprises a sensor assembly for measuring electromagnetic and/or other physical properties of solid and fluid materials within the annular space, in an underground formation surrounding the annular space and/or within the interior of the casing section, wherein the sensor assembly is mounted on a body of swellable material, which body is secured to the outer surface of the casing section and presses the sensor against the inner surface of the underground formation surrounding the wellbore after the casing string has been lowered into the wellbore.
 6. The system of claim 5, wherein the sensor assembly is mounted on a body of swellable elastomeric material.
 7. The system of claim 5, wherein the casing section is made of a non-magnetic or weakly magnetic material.
 8. The system of claim 7, where the non-magnetic or weakly magnetic material is selected from the group of materials consisting of: non-metallic materials, Glassfiber Reinforced Plastic_(GRP); non-magnetic materials, aluminium, gold, titanium;_low curie temperature materials, inconel 718, monel K500; low magnetic permeability soft magnetic materials, and casing steel grades L80 and L80 13 Chrome, where the relative magnetic permeability μ_(r) is in the range from 50 to 200 and/or the bulk electrical resistivity is in the range from 30×10⁻⁸ to 120×10⁻⁸ Ωm. 